Control device for vehicle and control method for vehicle

ABSTRACT

A control device for a vehicle is provided, which vehicle includes a driving source, and an automatic transmission having a torque converter provided downstream of the driving source in a power transmission path and having a lockup clutch, and an engaging element provided downstream of the torque converter in the power transmission path. The device includes a control unit which engages the engaging element in a state where the lockup clutch is engaged if an accelerator opening becomes not smaller than a predetermined opening during neutral running control in which the automatic transmission is brought into a power shut-off state during running of the vehicle.

TECHNICAL FIELD

The present invention relates to a control device for a vehicle and a control method for a vehicle.

BACKGROUND ART

JP2013-213557 discloses a control device for a vehicle adapted to execute so-called sailing-stop control in which, when a predetermined condition is met, a clutch is disengaged so that an automatic transmission is brought into a neutral state (power shut-off state) and a vehicle is made to run while a driving source is stopped.

SUMMARY OF INVENTION

In such a case where an acceleration intention is generated in a driver during execution of sailing-stop control, a driving force is preferably transmitted from a driving source to a driving wheel in response to the acceleration intention with favorable response.

Such a desire can occur not only when the sailing-stop control is to be cancelled but also when the driver has the acceleration intention during execution of neutral running control in general which disengages a clutch during running and brings an automatic transmission to a neutral state.

The present invention has an object to ensure acceleration response when an acceleration intention is generated in a driver during neutral running control.

In one aspect of the present invention, a device of controlling a vehicle is provided, which vehicle includes a driving source, and an automatic transmission having a torque converter provided downstream of the driving source in a power transmission path and having a lockup clutch, and an engaging element provided downstream of the torque converter in the power transmission path. In this aspect, the device includes a control unit which engages the engaging element in a state where the lockup clutch is engaged if an accelerator opening becomes not smaller than a predetermined opening during neutral running control in which the automatic transmission is brought into a power shut-off state during running of the vehicle.

In another aspect of the present invention, a method for controlling a vehicle is provided, which vehicle includes a driving source, and an automatic transmission having a torque converter provided downstream of the driving source in a power transmission path and having a lockup clutch, and an engaging element provided downstream of the torque converter in the power transmission path. In this aspect, the engaging element is engaged in a state where the lockup clutch is engaged if an accelerator opening becomes not smaller than a predetermined opening during neutral running control in which the automatic transmission is brought into a power shut-off state during running of the vehicle.

According to the aforementioned aspects, if the accelerator opening becomes not smaller than the predetermined opening during the neutral running control, acceleration response after the engaging element is engaged can be improved by engaging the engaging element in a state where the lockup clutch is engaged.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an outline configuration diagram of a vehicle according to an embodiment of the present invention.

FIG. 2 is a flowchart when sailing-stop control is cancelled in the embodiment.

FIG. 3 is a time chart when the sailing-stop control is cancelled in a comparative example.

FIG. 4 is a time chart when the sailing-stop control is cancelled in a first example.

FIG. 5 is a time chart when the sailing-stop control is cancelled in a second example.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described below by referring to the attached drawings. In the following, a speed ratio is a value obtained by dividing a rotation speed of an input shaft of a continuously variable transmission by a rotation speed of an output shaft of the continuously variable transmission.

FIG. 1 is an outline configuration diagram of a vehicle of this embodiment. The vehicle includes an engine 1, a torque converter 2, a forward/revere switching mechanism 3, a continuously variable transmission (variator) 4, a hydraulic control circuit 5, a mechanical oil pump 6 m, an electric oil pump 6 e, an engine controller 10, and a transmission controller 11.

In the vehicle, rotation generated in the engine 1 is transmitted to a driving wheel, not shown, via the torque converter 2, the forward/reverse switching mechanism 3, the continuously variable transmission 4, a gear set 8, and a differential gear device 9. That is, in a power transmission path with the engine 1 side as an upstream and a driving wheel side as a downstream, the rotation of the engine 1 is transmitted from the upstream to the downstream. An automatic transmission 15 is constituted by the torque converter 2, the forward/reverse switching mechanism 3 and the continuously variable transmission 4.

The torque converter 2 has a lockup clutch 2 a, and when the lockup clutch 2 a is engaged, an input shaft and an output shaft of the torque converter 2 are directly coupled, and the input shaft and the output shaft are rotated at the same speed.

The forward/reverse switching mechanism 3 has a double-pinion planetary gear set as a main constituent element and couples its sun gear to the engine 1 through the torque converter 2 and couples a carrier to a primary pulley 4 a. The forward/reverse switching mechanism 3 further includes a forward clutch 3 a for directly coupling the sun gear and the carrier of the double-pinion planetary gear set and a reverse brake 3 b for fixing a ring gear, transmits input rotation from the engine 1 via the torque converter 2 to the primary pulley 4 a as it is when the forward clutch 3 a is engaged, and transmits the input rotation from the engine 1 via the torque converter 2 to the primary pulley 4 a under reverse speed reduction when the reverse brake 3 b is engaged.

As states of the forward clutch 3 a and the reverse brake 3 b, there are “disengaged”, “standby”, “slip” and “engaged” states. These states are switched in accordance with a hydraulic pressure supplied to each piston pressure receiving chamber.

The “disengaged” is a state where the hydraulic pressure is not supplied to the forward clutch 3 a, and the forward clutch 3 a does not have a torque capacity, for example.

The “standby” is a state where the forward switch 3 a does not have a torque capacity though the hydraulic pressure is supplied to the forward clutch 3 a, for example. In the “standby” state, the forward clutch 3 a is in a state immediately before it has the torque capacity.

The “slip” is a state where the hydraulic pressure is supplied to the forward clutch 3 a, the forward clutch 3 a has the torque capacity, and a rotation speed difference considering a speed ratio R1 of the forward/reverse switching mechanism 3 when the forward clutch 3 a is engaged is generated between the input/output shafts of the forward/reverse switching mechanism 3, for example. In the “slip” state, the torque capacity is smaller than an input torque of the forward clutch 3 a.

The “engaged” is a state where the hydraulic pressure is supplied to the forward clutch 3 a, the forward clutch 3 a has the torque capacity, and the rotation speed difference considering the speed ratio R1 of the forward/reverse switching mechanism 3 when the forward clutch 3 a is engaged is not generated between the input/output shafts of the forward/reverse switching mechanism 3, for example. In the “engaged” state, the torque capacity is larger than an input torque of the forward clutch 3 a. The “engaged” state includes complete engagement in which the torque capacity has an allowance for the input torque by further increasing the torque capacity after the torque capacity becomes larger than the input torque of the forward clutch 3 a.

The continuously variable transmission 4 includes the primary pulley 4 a, a secondary pulley 4 b, and a belt 4 c. In the continuously variable transmission 4, the hydraulic pressure supplied to the primary pulley 4 a and the hydraulic pressure supplied to the secondary pulley 4 b are controlled so that a contact radius between each of the pulleys 4 a and 4 b and the belt 4 c is changed, and a speed ratio of the continuously variable transmission 4 is changed.

The mechanical oil pump 6 m is a mechanical oil pump to which rotation of the engine 1 is input and which is driven by using a part of power of the engine 1. Oil ejected from the mechanical oil pump 6 m by the driving of the mechanical oil pump 6 m is supplied to the hydraulic control circuit 5. When the engine 1 is stopped, the mechanical oil pump 6 m is not driven, and the oil is not ejected from the mechanical oil pump 6 m.

The electric oil pump 6 e is an electric-type oil pump driven by supply of electricity from a battery. By driving the electric oil pump 6 e if the mechanical oil pump 6 m is not driven, the oil can be supplied to the hydraulic control circuit 5 even while the engine is stopped.

The hydraulic control circuit 5 is constituted by a plurality of channels, a plurality of hydraulic actuators and the like. The hydraulic actuator is constituted by a solenoid and a hydraulic control valve. In the hydraulic control circuit 5, the hydraulic actuator is controlled on the basis of a control signal from the transmission controller 11, a supply path of the hydraulic pressure is switched, and a required hydraulic pressure is adjusted from a line pressure generated by oil ejected from the mechanical oil pump 6 m and the electric oil pump 6 e. The hydraulic control circuit 5 supplies the adjusted hydraulic pressure to each portion of the continuously variable transmission 4, the forward/reverse switching mechanism 3, and the torque converter 2.

The transmission controller 11 is constituted by a CPU, a ROM, a RAM and the like and controls an operation of the automatic transmission 15. In the transmission controller 11, a function of the transmission controller 11 is exerted by reading and executing a program stored in the ROM by the CPU. The engine controller 10 is also constituted similarly by a CPU, a ROM, a RAM and the like.

To the transmission controller 11, a signal from an accelerator pedal opening sensor 21 for detecting an accelerator pedal opening APO corresponding to an operation amount of an accelerator pedal 41, a signal from a brake fluid pressure sensor 22 for detecting a brake fluid pressure BRP corresponding to an operation amount of a brake pedal 42, and a signal from an inhibitor switch 23 for detecting a position of a shift lever 40 are input. Moreover, to the transmission controller 11, a signal from an engine rotation speed sensor 24 for detecting an engine rotation speed Ne which is a rotation speed of an output shaft of the engine 1, a signal from a primary rotation speed sensor 25 for detecting a primary rotation speed Npri which is a rotation speed of the primary pulley 4 a of the continuously variable transmission 4 (rotation speed on an output side of the forward/reverse switching mechanism 3), a signal from a vehicle speed sensor 26 for detecting a vehicle speed VSP, a signal related to an engine torque Te from the engine controller 10 controlling an operation of the engine 1 and the like are input.

In this embodiment, if a sailing-stop condition is met during running of a vehicle, the sailing-stop control is executed in which fuel injection to the engine 1 is stopped and the engine 1 is stopped, and the forward clutch 3 a and the reverse brake 3 b of the forward/reverse switching mechanism 3 are disengaged, and the automatic transmission 15 is brought into the neutral state. During the sailing-stop control, the lockup clutch 2 a is disengaged.

As a result, an inertia running distance in the state where the engine 1 is stopped is prolonged, and fuel efficiency of the engine 1 can be improved.

The sailing-stop conditions are as follows, for example:

(a) The shift lever 40 is at a D range.

(b) The vehicle speed VSP is not lower than a first predetermined vehicle speed V1.

(c) The accelerator pedal 41 has not been stepped on.

(d) The brake pedal 42 has not been stepped on.

The first predetermined vehicle speed V1 is a medium or high vehicle speed and is set in advance.

The sailing-stop condition is met when all the aforementioned (a) to (d) conditions are satisfied and is not met if any one of the aforementioned (a) to (d) is not satisfied.

If the sailing-stop condition is not met anymore during the sailing-stop control, the sailing-stop control is cancelled, the engine 1 is started, and the forward clutch 3 a is engaged. That is, the sailing-stop condition is also a sailing-stop cancellation condition for canceling the sailing-stop control. The sailing-stop condition and the sailing-stop cancellation condition may be different conditions.

When the sailing-stop cancellation condition is met, the engine 1 is started, and after the sailing-stop cancellation control for engaging the forward clutch 3 a is executed, normal running control is executed. In the sailing-stop cancellation control, after execution of rotation synchronization control in which the engine 1 is started and rotation speeds before and after the forward clutch 3 a are synchronized, engagement control for engaging the forward clutch 3 a is executed. The sailing-stop control, the sailing-stop cancellation control (rotation synchronization control, engagement control) and the like are executed by the transmission controller 11 and the engine controller 10.

During the sailing-stop control, the forward/reverse switching mechanism 3 is in the power shut-off state, and the automatic transmission 15 is in the neutral state. Moreover, since the engine 1 is stopped, the mechanical oil pump 6 m is not driven. Thus, during the sailing-stop control, a required hydraulic pressure is supplied to the vehicle by using the oil ejected from the electric oil pump 6 e.

Subsequently, a case where the sailing-stop control is to be cancelled will be described by using a flowchart in FIG. 2. When the processing illustrated in FIG. 2 is to be started, it is assumed that the sailing-stop control is being executed.

At Step S100, the transmission controller 11 determines whether the sailing-stop cancellation condition (SS cancellation condition) is met or not. Specifically, the transmission controller 11 determines whether any one of the aforementioned (a) to (d) is not satisfied anymore. If the sailing-stop cancellation condition is met, the processing goes to Step S101, while if the sailing-stop cancellation condition is not met, the processing this time is finished.

At Step S101, the transmission controller 11 determines whether the accelerator pedal opening APO is not smaller than a predetermined opening APO1 or not. The accelerator pedal opening APO is detected on the basis of a signal from the accelerator pedal opening sensor 21. The predetermined opening APO1 is an opening set in advance and is an opening by which determination that the acceleration intention of the driver is large can be made. Specifically, the predetermined opening APO1 is an opening at which kick-down control is executed in the automatic transmission 15 in the normal running control. If the accelerator pedal opening APO is not smaller than the predetermined opening APO1, the processing goes to Step S102. On the other hand, if the accelerator pedal opening APO is less than the predetermined opening APO1, the processing goes to Step S104.

The accelerator pedal opening APO can be substituted by another value in a correspondence relationship with an operation amount of the accelerator pedal 41 such as a throttle opening TVO, for example.

At Step S102, the transmission controller 11 and the engine controller 10 execute the sailing-stop cancellation control. Specifically, the transmission controller 11 engages the lockup clutch 2 a, and the engine controller 10 starts the engine 1. That is, an engagement instruction is output to the lockup clutch 2 a, and a start instruction of the engine 1 is output. As described above, in a state where the lockup clutch 2 a is engaged, the rotation synchronization control is executed. If the accelerator pedal opening APO is not smaller than the predetermined opening APO1 and the driver's acceleration intention is large, the lockup clutch 2 a is engaged before the forward clutch 3 a is rotation-synchronized.

At Step S103, the transmission controller 11 determines whether the forward clutch 3 a has rotation-synchronized or not. Specifically, the transmission controller 11 determines whether a relationship between the engine rotation speed Ne and the primary rotation speed Npri satisfies an equation (1) or not. The engine rotation speed Ne is detected on the basis of a signal from the engine rotation speed sensor 24. The primary rotation speed Npri is detected on the basis of a signal from the primary rotation speed sensor 25. |Ne−(R1×Npri)|≤N1  (1)

Reference character “R1” is a speed ratio of the forward/reverse switching mechanism 3 when the forward clutch 3 a is engaged. Reference character “N1” is a first threshold value set in advance and is a value at which such determination can be made that occurrence of an engagement shock can be suppressed when the forward clutch 3 a is engaged in a state where the lockup clutch 2 a is engaged. The first threshold value N1 is smaller than a second threshold value N2 which will be described later.

In this embodiment, since a turbine rotation speed of the torque converter 2 (a rotation speed Nin on an input side of the forward/reverse switching mechanism 3) is not detected, whether the forward clutch 3 a has rotation-synchronized or not is determined by using the engine rotation speed Ne and the primary rotation speed Npri.

If the equation (1) is satisfied, the transmission controller 11 determines that the forward clutch 3 a has rotation-synchronized, while if the equation (1) is not satisfied, it determines that the forward clutch 3 a has not rotation-synchronized. When the engine rotation speed Ne is heightened by the start of the engine 1 and it is determined that the forward clutch 3 a has rotation-synchronized, the processing goes to Step S106.

At Step S104, the engine controller 10 starts the engine 1. If the accelerator pedal opening APO is smaller than the predetermined opening APO1, the rotation synchronization control is executed in the state where the lockup clutch 2 a is disengaged.

At Step S105, the transmission controller 11 determines whether the forward clutch 3 a has rotation-synchronized or not. Specifically, the transmission controller 11 determines whether the relationship between the engine rotation speed Ne and the primary rotation speed Npri satisfies an equation (2) or not. |Ne−(R1×Npri)|≤N2  (2)

Reference character “N2” is a second threshold value set in advance and is a value at which it can be determined that occurrence of an engagement shock can be suppressed when the forward clutch 3 a is engaged in the state where the lockup clutch 2 a is disengaged. The second threshold value N2 is larger than the first threshold value N1.

If the equation (2) is satisfied, the transmission controller 11 determines that the forward clutch 3 a has rotation-synchronized, while if the equation (2) is not satisfied, it determines that the forward clutch 3 a has not rotation-synchronized. When the engine rotation speed Ne is heightened by the start of the engine 1 and it is determined that the forward clutch 3 a has rotation-synchronized, the processing goes to Step S106.

At Step S106, the transmission controller 11 finishes the rotation synchronization control and executes the engagement control. The transmission controller 11 heightens the hydraulic pressure supplied to the forward clutch 3 a and engages the forward clutch 3 a.

Subsequently, a case where the sailing-stop control is to be cancelled will be described by using a time chart. FIG. 3 is a time chart of a comparative example in which the accelerator pedal 41 is stepped on, the accelerator pedal opening APO becomes larger than the predetermined opening APO1, and the sailing-stop control is cancelled in a state where the lockup clutch 2 a is disengaged.

In this comparative example, the rotation speed Nin on the input side of the forward/reverse switching mechanism 3 is detected, and the rotation synchronization is determined on the basis of the input-side rotation speed Nin, the primary rotation speed Npri, and the speed ratio R1 of the forward/reverse switching mechanism 3 when the forward clutch 3 a is engaged. Specifically, if an equation (3) is satisfied, it is determined that the forward clutch 3 a has rotation-synchronized. |Nin−(R1×Npri)|≤N3  (3)

Reference character “N3” is a threshold value set in advance and is set so that occurrence of the engagement shock is suppressed when the forward clutch 3 a is engaged in the state where the lockup clutch 2 a is disengaged.

At time to, if the accelerator pedal 41 is stepped on and it is determined that the sailing-stop control cancellation condition is met, the sailing-stop cancellation control is started, and the rotation synchronization control is started. As a result, the engine 1 is started, and the engine rotation speed Ne and the input-side rotation speed Nin are increased. In FIG. 3, the engine rotation speed Ne is indicated by a solid line, and a part of the input-side rotation speed Nin is indicated by a broken line. In a range indicated by the broken line, since the lockup clutch 2 a is disengaged, the input-side rotation speed Nin is lower than the engine rotation speed Ne.

Moreover, when the rotation synchronization control is started, a standby pressure is supplied to the forward clutch 3 a as a preparation stage for quickly engaging the forward clutch 3 a, and a clutch stroke of the forward clutch 3 a is increased.

At time t1, if the equation (3) is satisfied and it is determined that the forward clutch 3 a has rotation-synchronized, the rotation synchronization control is finished, and the engagement control is started. By means of execution of the engagement control, an indicated pressure of the forward clutch 3 a rapidly rises, the clutch stroke increases, and the forward clutch 3 a is engaged.

At time t2, since the engagement control is finished, the sailing-stop cancellation control is finished, and the normal running control is started. Since the forward clutch 3 a has been engaged, the torque generated in the engine 1 is transmitted to the driving wheel, and the vehicle is accelerated. Moreover, when the forward clutch 3 a is engaged, the engagement of the lockup clutch 2 a is started at time t3.

As in the comparative example, when the accelerator pedal opening APO is larger than the predetermined opening APO1, if the lockup clutch 2 a is engaged after the engagement of the forward clutch 3 a, slip has been generated in the torque converter 2 when the running control is started. Thus, torque is not sufficiently transmitted from the engine 1 to the driving wheel, and a pulling shock occurs at acceleration. Moreover, acceleration response after the forward clutch 3 a is engaged is reduced. That is because if the forward clutch 3 a is engaged in the state where the lockup clutch 2 a is disengaged despite that the accelerator pedal opening APO is large, an influence of the slip becomes larger than torque amplification by the torque converter 2.

Moreover, when the accelerator pedal 41 is stepped on and the accelerator pedal opening APO becomes larger than the predetermined opening APO1, the kick-down control is normally executed, but if the kick-down control is executed at the vehicle speed VSP at which the sailing-stop control is executed, the lockup clutch 2 a is normally engaged. Thus, there is a concern that a sense of discomfort is given to the driver as compared with the case where the sailing-stop control is not executed.

On the other hand, as a first example of this embodiment, a case where the lockup clutch 2 a is engaged and rotation synchronization is executed, and the forward clutch 3 a is engaged will be described by using the time chart in FIG. 4.

At the time t0, when the accelerator pedal 41 is stepped on and it is determined that the sailing-stop cancellation condition is met, the engagement of the lockup clutch 2 a is started, the sailing-stop cancellation control is started, and the rotation synchronization control is started. As a result, the engine rotation speed Ne or the like increases similarly to FIG. 3. Here, since the lockup clutch 2 a is engaged, the input-side rotation speed Nin of the forward/reverse switching mechanism 3 matches the engine rotation speed Ne.

Moreover, since the standby pressure is supplied to the forward clutch 3 a, the clutch stroke of the forward clutch 3 a increases.

At the time t1, if the equation (3) is satisfied and it is determined that the forward clutch 3 a has rotation-synchronized, the rotation synchronization control is finished, and the engagement control is started. As a result, the forward clutch 3 a is engaged. When the lockup clutch 2 a is engaged and the forward clutch 3 a is engaged, if the rotation synchronization is determined under the condition similar to that in FIG. 3 in which the lockup clutch 2 a is not engaged, there is no slip by the torque converter 2 and the engine 1 acts as a load and thus, a pulling shock (engagement shock) occurs when the forward clutch 3 a is engaged.

At the time t2, since the engagement control is finished, the sailing-stop cancellation control is finished, and the normal running control is started.

As described above, when the lockup clutch 2 a is engaged and rotation synchronization is executed, and the forward clutch 3 a is engaged, the pulling shock as illustrated in FIG. 3 does not occur after the forward clutch 3 a is engaged, but the pulling shock occurs when the forward clutch 3 a is engaged. However, by engaging the forward clutch 3 a after the lockup clutch 2 a is engaged, since the lockup clutch 2 a is already in the engaged state when the running control is started, the acceleration response in the running control can be improved.

Subsequently, a second example of this embodiment will be described by using a time chart in FIG. 5. In FIG. 5, a part of a change of the rotation speed or the like in FIG. 4 is indicated by a dotted line for description.

At the time to, when the accelerator pedal 41 is stepped on and it is determined that the sailing-stop control cancellation condition is met, engagement of the lockup clutch 2 a is started, the sailing-stop cancellation control is started, and the rotation synchronization control is started. As a result, the engine rotation speed Ne and the like increase similarly to FIG. 4.

Moreover, since the standby pressure is supplied to the forward clutch 3 a, the clutch stroke of the forward clutch 3 a is increased.

At the time t1, if the equation (1) is satisfied and it is determined that the forward clutch 3 a has rotation-synchronized, the rotation synchronization control is finished, and the engagement control is started. As a result, the forward clutch 3 a is engaged.

Here, in the second example, as a threshold value at which the rotation synchronization is determined in the state where the lockup clutch 2 a is engaged, the first threshold value N1 different from the second threshold value N2 when the rotation synchronization is determined in the state where the lockup clutch 2 a is disengaged is set, or specifically, the first threshold value N1 is set smaller than the second threshold value N2. As a result, the rotation synchronization is determined in the state where the lockup clutch 2 a is engaged, and even if the forward clutch 3 a is engaged, occurrence of a pulling shock can be suppressed.

An effect of the embodiment of the present invention will be described.

When the sailing-stop control is to be cancelled, if the accelerator pedal opening APO is not smaller than the predetermined opening APO1, the forward clutch 3 a is engaged in the state where the lockup clutch 2 a is engaged. As a result, the acceleration response after the forward clutch 3 a is engaged is improved, the accelerator pedal opening APO is large, and the acceleration response when the acceleration intention is generated in the driver can be ensured.

When the sailing-stop control is to be cancelled, if the accelerator pedal opening APO is smaller than the predetermined opening APO1, the forward clutch 3 a is engaged in the state where the lockup clutch 2 a is disengaged. As a result, occurrence of an engagement shock can be suppressed when the forward clutch 3 a is engaged.

By executing the rotation synchronization control when the sailing-stop control is to be cancelled, the engagement shock when the forward clutch 3 a is engaged can be suppressed. In this embodiment, a sensor for detecting the input-side rotation speed Nin of the forward/reverse switching mechanism 3 is not provided, and the rotation synchronization is determined by using the engine rotation speed Ne and the primary rotation speed Npri.

In such a case, even if a rotation speed difference between the engine rotation speed Ne and the primary rotation speed Npri is the same, a rotation speed difference between before and after the forward clutch 3 a, that is, a rotation synchronization state is different depending on whether the lockup clutch 2 a is engaged or disengaged.

In this embodiment, the threshold value for determining the rotation synchronization is changed depending on whether the lockup clutch 2 a is engaged or disengaged. As a result, the rotation synchronization can be determined accurately regardless of the state of the lockup clutch 2 a, and occurrence of the engagement shock when the forward clutch 3 a is engaged can be suppressed.

Specifically, the first threshold value N1 at which the rotation synchronization is determined in the state where the lockup clutch 2 a is engaged is made smaller than the second threshold value N2 at which the rotation synchronization is determined in the state where the lockup clutch 2 a is disengaged. As a result, occurrence of the engagement shock when the forward clutch 3 a is engaged can be suppressed regardless of the state of the lockup clutch 2 a.

In addition to the constitution of the aforementioned embodiment, an accumulator may be provided in an oil path for supplying the hydraulic pressure to the forward clutch 3 a, for example. Alternatively, a dish plate may be provided between a piston for engaging the forward clutch 3 a in accordance with the hydraulic pressure and a plate.

In the aforementioned embodiment, the automatic transmission 15 having the forward/reverse switching mechanism 3 arranged on a front stage or on an upstream side of the continuously variable transmission (variator) 4 is described, but it may be applied to an automatic transmission having a sub-transmission mechanism arranged on a rear stage or on a downstream side of the continuously variable transmission 4. A power transmission mechanism is a concept including the forward/reverse switching mechanism 3, the sub-transmission mechanism, and other power transmission mechanisms. Moreover, a main transmission mechanism constituting the automatic transmission 15 is not limited to the belt continuously variable transmission 4 but may be a toroidal continuously variable transmission, and it is not limited to the continuously variable transmission but may be a stepped transmission.

In the aforementioned embodiment, as a method for determining whether the forward clutch 3 a has rotation-synchronized or not, the equation (1) and the equation (2) are used, but determination may be made from a viewpoint of a speed ratio by an equation (4) and an equation (5), for example. |R1−Ne/Npri|≤N4  (4) |R1−Ne/Npri|≤N5  (5)

Reference character “N4” is a fourth threshold value set in advance and is a value at which it can be determined that occurrence of the engagement shock can be suppressed when the forward clutch 3 a is engaged in the state where the lockup clutch 2 a is engaged. Reference character “N5” is a fifth threshold value set in advance and is a value at which it can be determined that occurrence of the engagement shock can be suppressed when the forward clutch 3 a is engaged in the state where the lockup clutch 2 a is disengaged and is larger than N4.

A method for determining whether the forward clutch 3 a has rotation-synchronized or not is not limited to the equation (1), the equation (2), the equation (4), and the equation (5) but it is only necessary that the rotation synchronization is determined accurately and occurrence of the engagement shock can be suppressed when the sailing-stop control is cancelled.

In the aforementioned embodiment, the sailing-stop control is described as an example of the neutral running control. However, the neutral running control may be sailing control or coast stop control, for example, other than the sailing-stop control. That is, the aforementioned control can be applied if the neutral cancellation condition is met and the forward clutch 3 a is engaged during the neutral running with the automatic transmission 15 in the neutral state.

The coast stop control is executed by the transmission controller 11 and the engine controller 10 when the coast-stop forming condition is met. The coast-stop forming conditions are the following (a) to (d), for example. The engine 1 which is a driving source is stopped during the coast stop control.

(a) The shift lever 40 is at the D range.

(b) The vehicle speed VSP is less than a second predetermined vehicle speed V2.

(c) The accelerator pedal 41 has not been stepped on.

(d) The brake pedal 42 has been stepped on.

Here, the second predetermined vehicle speed V2 is a low vehicle speed lower than the first predetermined vehicle speed V1.

The coast-stop forming condition is met when all the conditions (a) to (d) are satisfied and is not met if any one of (a) to (d) is not satisfied. Moreover, the coast-stop cancellation condition is that any one of (a) to (d) is not met during the coast-stop control, for example, but the coast-stop forming condition and the coast-stop cancellation condition may be different conditions.

The sailing control is executed by the transmission controller 11 and the engine controller 10 when the sailing forming condition is met. The sailing forming conditions are the following (a) to (d), for example. During the sailing control, the engine 1 which is a driving source is not stopped:

(a) The shift lever 40 is at the D range.

(b) The vehicle speed VSP is not lower than the second predetermined vehicle speed V2.

(c) The accelerator pedal 41 has not been stepped on.

(d) The brake pedal 42 has not been stepped on.

The sailing forming condition is met when all the conditions (a) to (d) are satisfied and is not met if any one of (a) to (d) is not satisfied. Moreover, the sailing cancellation condition is that any one of (a) to (d) is not met during the sailing control, for example, but the sailing forming condition and the sailing cancellation condition may be different conditions.

In the aforementioned embodiment, the lockup clutch 2 a is disengaged during the sailing stop control, but if the sailing-stop condition is met in the state where the lockup clutch 2 a is engaged, the state where the lockup clutch 2 a is engaged during the sailing stop control may be maintained. As a result, there is no need to engage the lockup clutch 2 a when the sailing-stop control is cancelled, the number of engaging times of the lockup clutch 2 a can be reduced, and durability of the lockup clutch 2 a can be improved.

If such neutral running control (sailing-stop control) is to be executed, if the predetermined neutral running control cancellation condition is met, the lock up clutch 2 a is disengaged, and the forward clutch 3 a is engaged in the state where the lockup clutch 2 a is disengaged.

The “predetermined neutral running control cancellation condition” is not limited, but at least one of the following (a) to (c) conditions can be included, for example. As a result, since the forward clutch 3 a is engaged in the state where the lockup clutch 2 a is disengaged, the engagement shock of the forward clutch 3 a can be reduced.

(a) The accelerator pedal 41 is stepped on, and the accelerator pedal opening APO is smaller than the predetermined opening APO1 (0<APO<APO1).

(b) The brake pedal 42 is stepped on.

(c) The vehicle speed VSP is less than the first predetermined vehicle speed V1 (VSP<V1).

A condition other than (a) to (c) can be added as a neutral running control cancellation condition, and the added condition (d) in that case is whether the road has a predetermined gradient or not (entering an ascending road or not) or a gear position is changed to a low-speed range (L range, S range) or not, for example. And when any one of the conditions (a) to (d) is met during the neutral running control, it is determined that the neutral running control cancellation condition is met.

To include at least the (a) condition as the predetermined neutral running control cancellation condition is preferable from a viewpoint of prevention of the engagement shock.

In the coast-stop control, the cases (b) the brake pedal 42 is stepped on, and (c) the vehicle speed VSP becomes less than the first predetermined vehicle speed V1 are not included in the predetermined coast-stop control cancellation condition.

In the aforementioned embodiment, the case where the engine 1 is a driving source is described. However, the driving source is not limited to the engine 1 but may be a motor, for example, or a combination of the engine 1 and the motor.

In the aforementioned embodiment, the case where the transmission controller 11 and the engine controller 10 are constituted as separate controllers is described. However, functions of the transmission controller 11 and the engine controller 10 may be integrated and constituted as a single controller. Moreover, at least either one of the transmission controller 11 or the engine controller 10 may be constituted by a plurality of controllers.

Forms derived from the aforementioned explanation other than those described in claims will be cited below.

A control device for an automatic transmission connected to a driving source, having a torque converter provided closer to a downstream side of a power transmission path than the driving source and having a lockup clutch and an engaging element provided closer to the downstream side of the power transmission path than the torque converter and disposed capable of shutting off transmission of power through the automatic transmission, in which neutral running control for bringing the automatic transmission into a power shut-off state when a predetermined neutral running condition is met is executed and at cancellation based on an increase of an accelerator pedal opening of the neutral running control in a state where a lockup clutch is disengaged, the engaging element is engaged in a state where the lockup clutch is engaged during running of a vehicle.

A control device for an automatic transmission in which the engaging element is engaged after engagement of the lockup clutch at the cancellation of the neutral running control.

A control device for an automatic transmission in which, if an accelerator pedal opening increases to not smaller than a predetermined opening, the lockup clutch is engaged, and if the accelerator pedal opening is less than the predetermined opening, the state where the lockup clutch is disengaged is maintained at the cancellation of the neutral running control.

A control device for an automatic transmission which maintains a state where the lockup clutch is engaged during the neutral running control if the lockup clutch is in the engaged state when the neutral running condition is met.

The embodiment of the present invention has been described above, but the explanation of the aforementioned embodiment merely illustrates a part of an application example of the present invention and is not intended to limit the technical scope of the present invention to the specific configuration of the aforementioned embodiment.

This application claims a priority based on Japanese Patent Application No. 2016-019759 filed with the Japanese Patent Office on Feb. 4, 2016, the entire contents of which is incorporated herein by reference. 

The invention claimed is:
 1. A device of controlling a vehicle having: a driving source; and an automatic transmission having a torque converter provided downstream of the driving source in a power transmission path and having a lockup clutch, and an engaging element provided downstream of the torque converter in the power transmission path, the device comprising: a control unit adapted to execute rotation synchronization of the engaging element in a state where the lockup clutch is engaged if an accelerator opening becomes not smaller than a predetermined opening during neutral running control in which the automatic transmission is brought into a power shut-off state during running of the vehicle, and to start engagement of the engaging element when the rotation synchronization of the engaging element is finished.
 2. The device according to claim 1, wherein the control unit maintains, if the lockup clutch is in an engaged state before the neutral running control, a state where the lockup clutch is engaged during the neutral running control.
 3. The device according to claim 1, wherein the control unit engages, if a predetermined neutral running control cancellation condition is met, the engaging element in a state where the lockup clutch is disengaged.
 4. The device according to claim 3, wherein the control unit executes the rotation synchronization when the engaging element is engaged from a state where the neutral running control is executed, and determines the rotation synchronization when the engaging element is engaged in a state where the lockup clutch is disengaged and the rotation synchronization when the engaging element is engaged in a state where the lockup clutch is engaged with different threshold values.
 5. The device according to claim 4, wherein a first threshold value at which the rotation synchronization is determined when the engaging element is engaged in the state where the lockup clutch is engaged is smaller than a second threshold value at which the rotation synchronization is determined when the engaging element is engaged in the state where the lockup clutch is disengaged.
 6. A method for controlling a vehicle having: a driving source; and an automatic transmission having a torque converter provided downstream of the driving source in a power transmission path and having a lockup clutch, and an engaging element provided downstream of the torque converter in the power transmission path, the method comprising: executing rotation synchronization of the engaging element in a state where the lockup clutch is engaged if an accelerator opening becomes not smaller than a predetermined opening during neutral running control in which the automatic transmission is brought into a power shut-off state during running of the vehicle; and starting engagement of the engaging element when the rotation synchronization of the engaging element is finished.
 7. A device of controlling a vehicle having: a driving source; and an automatic transmission having a torque converter provided downstream of the driving source in a power transmission path and having a lockup clutch, and an engaging element provided downstream of the torque converter in the power transmission path, the device comprising: a control unit adapted to: engage the engaging element in a state where the lockup clutch is engaged if an accelerator opening becomes not smaller than a predetermined opening during neutral running control in which the automatic transmission is brought into a power shut-off state during running of the vehicle; engage, if a predetermined neutral running control cancellation condition is met, the engaging element in a state where the lockup clutch is disengaged; and execute rotation synchronization when the engaging element is engaged from a state where the neutral running control is executed, wherein the control unit determines the rotation synchronization when the engaging element is engaged in a state where the lockup clutch is disengaged and the rotation synchronization when the engaging element is engaged in a state where the lockup clutch is engaged with different threshold values.
 8. A device of controlling a vehicle having: a driving source; and an automatic transmission having a torque converter provided downstream of the driving source in a power transmission path and having a lockup clutch, and an engaging element provided downstream of the torque converter in the power transmission path, the device comprising: means for executing rotation synchronization of the engaging element in a state where the lockup clutch is engaged if an accelerator opening becomes not smaller than a predetermined opening during neutral running control in which the automatic transmission is brought into a power shut-off state during running of the vehicle; and means for starting engagement of the engaging element when the rotation synchronization of the engaging element is finished. 